In the printing industry, it is typical to stack the papers that have just been run off of the printing press. This often results in impressions of ink on the back of the next piece of paper in the stack, a problem known in the industry as "offset." The usual practice to avoid offset has been the use of a spray powder that is applied between the papers to be stacked, which serves to temporarily cushion wet ink on one delivered sheet from the next sheet. This cushioning prevents offset by separating the sheets long enough to allow the ink to "set up."
There are, however, drawbacks to using powder. Different powders are required on different prints, and it is necessary to keep the assorted powders in stock and exercise judgment in the selection of the proper powder for a particular job. Systems utilizing the spray powder fill the work area with dust, and this dust often becomes embedded on everything in the area. The powder has a tendency to collect on the workings of the press, as well as on equipment in other parts of the shop, causing mechanical breakdowns and jammings. The result in extra maintenance and repair costs, as well as lost profits in press down time. Systems employing powder may also be a potential health hazard in that the powder may end up being inhaled by the operator of the printing press.
The powder does not dry the ink, rather, it suspends the sheets to allow them to dry without causing offset. The subsequent drying is a slow process and it is typical to have numerous stacks around a print shop being allowed to dry before distribution to customers. Print jobs that involve multiple colors cannot be run quickly and cleanly because the powder becomes an intermediary between the paper and the second color ink.
To remedy the problems inherent with the use of spray powder, attempts have been made to introduce infrared dryers as a means of drying the ink. Though manufacturers have successfully incorporated infrared dryers in larger printing presses, problems have developed in attempting to adapt the dryers to smaller sheet-fed units. The biggest drawback is heat build-up, causing the potential for burns to operators, melted electrical connections, and fires within the press itself. Excessive heat may also thin the ink, resulting in an inferior product.